Field of the Invention
This invention generally relates to a bicycle sprocket assembly. More specifically, the present invention relates to a bicycle sprocket assembly including four sprockets attached to a sprocket supporting member.
Background Information
Most bicycles utilize a chain drive transmission in which a chain is moved between a plurality of front sprockets and a plurality of rear sprockets to change gears. In recent years, bicycle component manufacturers have been manufacturing bicycle transmissions that have more available speeds to the rider. As the available speeds in the bicycle transmission increases, the number of sprockets installed on the rear wheel also usually increases. Accordingly, various attempts have been made in order to increase the maximum number of sprockets that can be installed on a rear hub assembly. For example, some multiple sprocket assemblies use a spider (sprocket supporting member), which supports a plurality of ring-shaped sprocket wheels on a freewheel of a rear hub. In order to reduce an overall weight of the multiple sprocket assembly that uses a spider, a light metal, such as aluminum, etc., is generally used for the spider, while various types of steel materials are used for the sprockets to provide adequate strength. One example of a. multiple sprocket assembly that uses a spider is disclosed in U.S. Pat. No. 6,382,381 (assigned to Shimano Inc.).